by Chris Kelly, Founder, AbScent 

If you have heard anything at all about smell training, you have probably heard
about the four essential oils recommended: lemon, rose, clove and eucalyptus.
I’d like to write a bit here about how they were originally chosen, and how they have
become the four oils of choice for smell training.

A book was written in 1915 by a German psychologist called simply “Der Geruch”
(Smell). This is a lengthy discourse written in an attempt to understand smells and
pin them down. The author tried to classify smells, and see where the main
groupings intersected, and also which smells overpower other smells (onion and
camphor for instance. Hardly a fair fight). Would comparing and contrasting smells
could lead to anything meaningful? It all seems a bit out of date now—you can
download a pdf copy through Google books—but you can see that there was a
genuine attempt to understand not so much the “sense of smell” as smells in general.

The comment that I thought was most memorable comes in the foreword: “the
composition of a perfume cannot depend upon objective chemical
characteristics, but must take into account subjective, emotional effects”. This
comment interests me because as a largely recovered post-viral anosmic, the thing
that shines through loud and clear when I smell perfume is an unemotional
understanding of individual constituents, but the poetry and emotional impact of the
combination is largely lost on me.

So how did this book lead us forward into the 21st century to smell training with
lemon, rose, clove, and eucalyptus? Henning theorises about a prism of smells,
defining six groupings: floral, putrid, fruity, burned, spicy and resinous. If you
imagine a column with three sides, and one of these smell designations at each
corner, you will have a picture in your mind of the author’s smell prism.

Fast forward to the dawn of smell training as a therapy for people with smell loss.
Given that smell training with something putrid and something burned would be
inconvenient and probably unpleasant, the four remaining smell groups were left:
floral (rose), fruity (lemon), spicy (clove) and resinous (eucalyptus).

Because of the way scientific research works, these four essential oils were reused in
many of the subsequent studies on smell training. Using the same oils kept a level
playing field when considering how patients were responding. And so these four
oils became the norm for smell training.

When I started smell training, I was unable to detect rose at all. Clove was so
revolting to me that I had to really steel myself to do it. In time it became bearable
and now is pleasant. Lemon was the first that felt real to me, it was the first where I
felt I could say “this smells the way I expect it to smell, or sort of”. Eucalyptus always
packed a big trigeminal punch for me. It’s that blast of Vicks you get when you try it,
and it is important to say that the trigeminal response is not smell—this is another
nerve at work inside your nose alerting you to a sensation rather than an odour.

When people ask me whether it is important to use these four oils or whether they
should feel free to try others, I always say they should feel free to smell train freely
with whatever they feel makes them happiest. The classic four, first described by
Professor Hummel in 2009, are just the most frequently described in the
literature. The golden rules are: Do it twice daily. Do it mindfully. And try not to
shy away from smells that have become disgusting through parosmia. Boxing
your way through the bad smells seems to be, from my own experience and that of
others in this group, the best way to get around the misery of parosmia.

Now if I can borrow the words of Nancy Rawson in another blog post: go forth and
smell!

October 22, 2017